Method of forming honeycomb panel

ABSTRACT

A method of forming honeycomb panels of high strength material whereby the panel to be formed is positioned between an inner metallic cover sheet and an outer sheet of resilient material. The sandwich pack so formed is disposed between die set members which are moved relative to each other to deform the pack. During the forming operation, the edge portions of individual honeycomb cores bite into the bonding surface of the resilient cover sheet material which functions as a structural restraint to minimize dimensional failure by preventing the spreading apart of adjacent cores one from another on the tension side of the bend. All of the bending of the panel is taken in uniform deformation on the compression side of the panel.

United States Patent Almond [451 June 20, 1972 METHOD OF FORMING HONEYCOPANEL 1 Inventor:

US. Cl. ..29/423, 29/428, 29/DlG. l, 29/DlG. 3, 29/DlG. 9, 29/455 LM,72/54 Int. Cl ..B23p 17/00 Field of Search... .29/423, 428, 421, 432,DlG. l, 29/DIG. 3, D10. 9, 420, 455 LM; 72/54, 57, 60

References Cited UNITED STATES PATENTS 10/1958 Wheeler ..29/DlG, 3

6/1961 Hall 10/1962 Watter Allingham ..29/DIG. 1

3,460,233 8/1969 Pfaffenberger ..29/423 Primary Examiner-John F.Campbell Assistant Examiner-Donald P. Rooney Attorney-Thomas l.Davenport, Edward M. Farrell, John D.

Sowell, Alford L. Trueax, Jr. and William R. Nolte [57] ABSTRACT Amethod of forming honeycomb panels of high strength material whereby thepanel to be formed is positioned between an inner metallic cover sheetand an outer sheet of resilient material. The sandwich pack so formed isdisposed between die set members which are moved relative to each otherto deform the pack. During the forming operation, the edge portions ofindividual honeycomb cores bite into the bonding surface of theresilient cover sheet material which functions as a structural restraintto minimize dimensional failure by preventing the spreading apart ofadjacent cores one from another on the tension side of the bend. All ofthe bending of the panel is taken in uniform deformation on thecompression side of the panel.

3 Claims, 2 Drawing Figures METHOD OF FORMING HONEYCOMB PANEL Thepresent invention relates to a method for deforming high strength planarmetallic honeycomb core membersinto compound curve form by theapplication of pressure between opposed die-set members. Moreparticularly, the present invention relates to a method for deformingpanel honeycomb members in compound curve form by the application ofpressure between opposed die-set members wherein the application of aresilient bonding sheet to an outer surface of core panel permitsdeforming without destroying the honeycomb core member or introducingdeleterions stress patterns therein.

The invention will be more readily understood by reference I to theaccompanying specification and drawing wherein:

FIG. 3 is a sectional view taken along the lines 3-3 of FIG. I

2 illustrating the relationship between the outer resilient sandwichcover sheet and edge portions of adjacent cores of the honeycomb panel.Y

Honeycomb metal core panels having high strength an which are highlyresistant to deformation may be deformed in accordance with the presentinvention by a procedure wherein crushing and deforming stresses in thedeformed panel are confined to one side of the panel. The inventionmethod involves the application, of a resilient cover sandwich sheet tothe outer edge portions of the cores adjacent to the tension surface ofthe honeycomb panel whereby separation between adjacent cores of thepanel on the tension side of the bend is prevented and all of thedeformation is uniformly confined to the compression side of the panel.

With reference now to FIG. 1 of the drawings there is shown in explodedrelation a sandwich arrangement including a central honeycomb panel 11,a top cover member 13, and a lower resilient sheet of material 15. Thehoneycomb panel 11 shown is illustrated as being of planar form andhaving characteristics of being highly resistant to bending ordeformation. The panel 11 may be of conventional construction and in thepresent instance includes cells 17 formed of metal such as aluminum.While the cells are illustrated in the present instance as beinghexagonal in form it is to be understood that the same may be of otherpatterns such as square, rectangular, cylindrical, and the like. 'Theaforementioned top cover sheet rests upon the top edge portions 19 ofthe cells of the panel, while the lower edge portions 21 of the cellsengage the lower resilient sheet 15. The latter sheet is adhered to thelower edges 21 by means of a suitable form of contact cement 23 carriedon its upper face. The lower resilient cover sheet may be of resilientplastic material such as a form of vinyl. In the arrangement shown thetop edge portions 19 of the honeycomb panel 11 corresponds to itscompression side, while the lower edge portions 21 of the cellscorrespond to its tension side when the same is deformed by die-setmeans 24 shown in FIG. 2. The resilient lower cover sheet 15 moreoverhas a tensile strength which exceeds the compressive forces adjacent thecompressive side 12 of the panel 11 when the same is subjected toforming in the die-set means illustrated in FIG. 2. The die-set means 24comprise a male die member and a female die member 26 with a cavity 28.In the present instance the male die member is shown in cylindrical formbut may be of a compound or reverse compound curve form while the femaledie 26 may be of a complemental construction to accept such compoundcurve form.

In the operation of the deforming process, after adhering the bottomcover sheet 15 to the lower side of the honeycomb panel 11 with theadhesive 23, the panel 11 with lower cover adhered thereto is placedacross the top of the female die part 26 of the die-set means 23 to spanthe cavity 28 in its top surface. When so positioned the lower coversheet 15 contacts the upper flat surface 27 of the female die. The topcover member 13 is then placed on the top of the panel 11 whereupon themale member 25 is moved toward the female member 26 to deform the corepanel 11 therebetween. During this action the top portion 12 of thehoneycomb panel undergoes lateral forces .tending to deform it incompression so that width of the cells 17 is less adjacent their topedge portions 17, than along their lower edge portions as at 24. The topmarginal edges 19 of the cores or cells of the honeycomb are enabled toslide relative to the aluminum sheet 13 to deform by uniformly crushingslightly in compression. Due to the lower resilient cover sheet 15, thelower edge portions of the cells 17 are restrained against separationadjacent the edge portions 14 by virtue of the locking engagement ofsaid edge portions with said resilient sheet 15.

Referring now to FIG. 3 it is seen that the lower edge portions 21 ofthe individual cells 17 bite into and indent the top surface of coversheet 15 .as indicated by the depressed portions as at 31. Inasmuch asthe tension capability of the sheet 15 exceeds the force required tocrush the top portions 19 of the cells 17 in compression, practicallyall of the deformation of the honeycomb panel occurs adjacent the topportion 19 of the panel and tension deformation adjacent the tensionside 21 is thereby minimal. Upon the panel 11 being so formed the maleand female die members 25 and 26 respectively are pulled apart to enablelifting off of the cover sheet 13, and upon removal of panel 11 andlower cover sheet 15 adhered thereto, the latter may be peeled offleaving the panel 11 of the desired form.

While the invention has been described in detail in the foregoingspecification and the drawing similarly illustrates the same, it will beobvious to those skilled in the art that vari ous changes andmodifications may be made therein. By way of example it has been foundthat under certain circumstances the upper cover sheet 13 may be.omitted from the above described steps. It is aimed therefore to coverall such changes hering one surface of said sheet of plastic material tosaid tension side of said panel with a cement, providing a die-sethaving a male member and a female member with a cavity therein, placingsaid panel with said plastic sheet adhered thereto with the latter incontact with said female member and bridging said cavity, applying saidmale die to the compression side of said panel to force said panel intosaid cavity.

2. In the method as set forth in claim 1 including the step of providingsaid sheet of plastic material with a deformable surface to engage saidedge portions defining its tension side, whereby upon applying said maledie to said compression side of said panel to force said panel into saidcavity, said edges of said cells adjacent said tension side of saidpanel are caused to penetrate said deformable surface to interlocktherewith to thereby structurally restrain adjacent cells along saidtension side against movement.

3. In the method as set forth in claim 1 and including the step ofproviding a sheet of metal, placing said sheet of metal on saidcompression side of said panel after adhering said sheet of plasticmaterial to said tension side, whereby upon said panel being forcedwithin the cavity of said female die by said male die, said edgeportions adjacent said compression side are caused to slide relative tosaid-sheet of metal thereby enabling said cells to uniformly falladjacent said compression side of said panel.

0: k t t a:

1. The method of forming a honeycomb panel having a multiplicity ofcells having edge portions defining a compression side and aN oppositetension side, comprising the steps of, providing a sheet of plasticmaterial having a tensile strength which exceeds the compressive forcesrequired to laterally crush the cells of said panel adjacent itscompressive side, adhering one surface of said sheet of plastic materialto said tension side of said panel with a cement, providing a die-sethaving a male member and a female member with a cavity therein, placingsaid panel with said plastic sheet adhered thereto with the latter incontact with said female member and bridging said cavity, applying saidmale die to the compression side of said panel to force said panel intosaid cavity.
 2. In the method as set forth in claim 1 including the stepof providing said sheet of plastic material with a deformable surface toengage said edge portions defining its tension side, whereby uponapplying said male die to said compression side of said panel to forcesaid panel into said cavity, said edges of said cells adjacent saidtension side of said panel are caused to penetrate said deformablesurface to interlock therewith to thereby structurally restrain adjacentcells along said tension side against movement.
 3. In the method as setforth in claim 1 and including the step of providing a sheet of metal,placing said sheet of metal on said compression side of said panel afteradhering said sheet of plastic material to said tension side, wherebyupon said panel being forced within the cavity of said female die bysaid male die, said edge portions adjacent said compression side arecaused to slide relative to said sheet of metal thereby enabling saidcells to uniformly fall adjacent said compression side of said panel.